1. Field of the Invention
The present invention relates to a control apparatus and an adjustment method for a vibratory actuator configured to actuate one driven member with use of a plurality of vibrators.
2. Description of the Related Art
Conventionally, there has been known a vibratory actuator configured to drive a driven member by causing an elliptic motion at a predetermined mass point. A vibratory actuator has such a characteristic that it can realize high torque drive while generating only low noises. By making use of this characteristic, it is proposed to employ a vibratory actuator configured to drive a circular slider with use of a plurality of vibrators as an actuation means in a lens barrel or the like.
However, if there is a variation among the characteristics of the individual vibrators, a predetermined torque cannot be obtained or the drive characteristic of the actuator may be adversely influenced. Therefore, the characteristics of the individual vibrators need to be adjusted.
In this connection, Japanese Patent Application Laid-Open No. 1-227669 and Japanese Patent No. 3248545 discuss a technique for adjusting the characteristics of a plurality of vibratory actuators. Japanese Patent Application Laid-Open No. 1-227669 discusses a configuration allowing adjustment of a pressure applied between a rotor and a stator so that a plurality of vibratory actuators have a same resonance frequency. On the other hand, Japanese Patent No. 3248545 discusses detection of a difference among outputs of a plurality of vibratory actuators to adjust the characteristics of the plurality of vibratory actuators based on this difference.
Both Japanese Patent Application Laid-Open No. 1-227669 and Japanese Patent No. 3248545 involve an actuator configured to drive one rotor by one stator, and in these cases, it is probably not so difficult to measure the characteristics of the individuals of such vibratory actuators.
However, in the case of an actuator configured to drive one slider by a plurality of vibrators, driving of one vibrator may be insufficient to drive the slider due to a lack of torque power, resulting in a failure to measure the characteristics of the individual vibrators. Therefore, in this case, the characteristics of the individual vibrators should be adjusted before they are installed into the actuator, but it is troublesome and hard to adjust the vibrators and then install them one by one.